// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_FILES_FILE_PROXY_H_
#define BASE_FILES_FILE_PROXY_H_

#include <stdint.h>

#include "base/base_export.h"
#include "base/callback_forward.h"
#include "base/files/file.h"
#include "base/files/file_path.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"

namespace tracked_objects {
class Location;
};

namespace base {

class TaskRunner;
class Time;

// This class provides asynchronous access to a File. All methods follow the
// same rules of the equivalent File method, as they are implemented by bouncing
// the operation to File using a TaskRunner.
//
// This class performs automatic proxying to close the underlying file at
// destruction.
//
// The TaskRunner is in charge of any sequencing of the operations, but a single
// operation can be proxied at a time, regardless of the use of a callback.
// In other words, having a sequence like
//
//   proxy.Write(...);
//   proxy.Write(...);
//
// means the second Write will always fail.
class BASE_EXPORT FileProxy : public SupportsWeakPtr<FileProxy> {
public:
    // This callback is used by methods that report only an error code. It is
    // valid to pass a null callback to some functions that takes a
    // StatusCallback, in which case the operation will complete silently.
    typedef Callback<void(File::Error)> StatusCallback;

    typedef Callback<void(File::Error,
        const FilePath&)>
        CreateTemporaryCallback;
    typedef Callback<void(File::Error,
        const File::Info&)>
        GetFileInfoCallback;
    typedef Callback<void(File::Error,
        const char* data,
        int bytes_read)>
        ReadCallback;
    typedef Callback<void(File::Error,
        int bytes_written)>
        WriteCallback;

    FileProxy();
    explicit FileProxy(TaskRunner* task_runner);
    ~FileProxy();

    // Creates or opens a file with the given flags. It is invalid to pass a null
    // callback. If File::FLAG_CREATE is set in |file_flags| it always tries to
    // create a new file at the given |file_path| and fails if the file already
    // exists.
    //
    // This returns false if task posting to |task_runner| has failed.
    bool CreateOrOpen(const FilePath& file_path,
        uint32_t file_flags,
        const StatusCallback& callback);

    // Creates a temporary file for writing. The path and an open file are
    // returned. It is invalid to pass a null callback. The additional file flags
    // will be added on top of the default file flags which are:
    //   File::FLAG_CREATE_ALWAYS
    //   File::FLAG_WRITE
    //   File::FLAG_TEMPORARY.
    //
    // This returns false if task posting to |task_runner| has failed.
    bool CreateTemporary(uint32_t additional_file_flags,
        const CreateTemporaryCallback& callback);

    // Returns true if the underlying |file_| is valid.
    bool IsValid() const;

    // Returns true if a new file was created (or an old one truncated to zero
    // length to simulate a new file), and false otherwise.
    bool created() const { return file_.created(); }

    // Claims ownership of |file|. It is an error to call this method when
    // IsValid() returns true.
    void SetFile(File file);

    File TakeFile();

    PlatformFile GetPlatformFile() const;

    // Proxies File::Close. The callback can be null.
    // This returns false if task posting to |task_runner| has failed.
    bool Close(const StatusCallback& callback);

    // Proxies File::GetInfo. The callback can't be null.
    // This returns false if task posting to |task_runner| has failed.
    bool GetInfo(const GetFileInfoCallback& callback);

    // Proxies File::Read. The callback can't be null.
    // This returns false if |bytes_to_read| is less than zero, or
    // if task posting to |task_runner| has failed.
    bool Read(int64_t offset, int bytes_to_read, const ReadCallback& callback);

    // Proxies File::Write. The callback can be null.
    // This returns false if |bytes_to_write| is less than or equal to zero,
    // if |buffer| is NULL, or if task posting to |task_runner| has failed.
    bool Write(int64_t offset,
        const char* buffer,
        int bytes_to_write,
        const WriteCallback& callback);

    // Proxies File::SetTimes. The callback can be null.
    // This returns false if task posting to |task_runner| has failed.
    bool SetTimes(Time last_access_time,
        Time last_modified_time,
        const StatusCallback& callback);

    // Proxies File::SetLength. The callback can be null.
    // This returns false if task posting to |task_runner| has failed.
    bool SetLength(int64_t length, const StatusCallback& callback);

    // Proxies File::Flush. The callback can be null.
    // This returns false if task posting to |task_runner| has failed.
    bool Flush(const StatusCallback& callback);

private:
    friend class FileHelper;
    TaskRunner* task_runner() { return task_runner_.get(); }

    scoped_refptr<TaskRunner> task_runner_;
    File file_;
    DISALLOW_COPY_AND_ASSIGN(FileProxy);
};

} // namespace base

#endif // BASE_FILES_FILE_PROXY_H_
